A BIP, or Behavior Improvement Plan is a required part of an IEP (Individual Education Plan) if the behavior box is checked off where it asks whether communication, vision, hearing, behavior and/or mobility effect academic achievement. If a child's behavior disrupts the classroom and significantly interrupts his or her education, then a BIP is very much in order.
Usually a special education teacher, a behavior analyst or a school psychologist will perform an FBA and using that information, write a document that describes target behaviors, replacement behaviors or behavioral goals, the procedure for changing or extinguishing the target behaviors, measures for success, and the people who will be responsible for instituting and following through on the BIP. For more, read the article on the BIP

